1. Field of the Invention
The present invention relates to a duct and a process for producing the same. More specifically, it relates to a duct having a simple structure and capable of suppressing occurrences of an intake noise and a dropping-out of an adsorbent, and to a process for producing the same capable of producing easily.
2. Related Art
Conventionally, an intake duct provided with a fuel vapor absorption function so as to reduce an emitted fuel vapor outside the vehicle from a carburetor via an air cleaner when the vehicle engine is stopped, is disclosed, for example in JP-A S58-72669 and JP-U1 S56-41149.
However, according to JP-A S58-72669 above, a porous adsorbing layer is attached to an inner wall of a duct body such that a forming process of the duct body and a fixing process of the porous adsorbing layer must be carried out separately. Further, according to JP-U1 S56-41149, a container accommodating a fuel vapor adsorbing layer is attached to an opening part that is formed on an outer circumferential side of a duct body, such that the duct itself must be made large and a relatively large installation space in an engine compartment is necessary. In addition, though a trapping wall is provided on the lower portion of the inner wall of the duct body for trapping a fuel vapor with a relatively higher density than that of air, the trapping wall sometimes leads to an increased suction resistance of an outdoor air and to a reduced engine power. Moreover, a forming process of the duct body and a fixing process of the porous adsorbing layer must be carried out separately in a manner substantially similar to the case in JP-A S58-72669.
Thus, an intake duct formed from a nonwoven fabric comprising an adsorbent for solving the problems above is proposed, for example in JP-A 2006-90252.
JP-A 2006-90252 above discloses a production method comprising production steps for a nonwoven fabric with an adsorbent dyed fiber and for a duct using the nonwoven fabric, successively. Additionally, a production method comprising a manufacturing process for a nonwoven fabric and a coating process where an adsorbent is coated on the duct.
According to the former method, since an adsorbent dyed fiber is used, it is difficult to adhere these fibers together. Therefore, in this method, the duct is formed by fulling the nonwoven fabric disposed on an outer circumference of a wire. Further, according to the latter method, since the adsorbent is coated, there may be a case where permeability is inhibited and a case where the adsorbent is removed from a fiber of the nonwoven fabric due to a long-term use.